Multi-panel blank with parallel panel axes for a collapsible field director structure

ABSTRACT

A blank for forming a collapsible field director structure comprises nonconductive material sheet having at least three panels thereon, one panel being a master panel and the other two panels being slave panels. Each panel is substantially rectangular in shape and has elongated upper and lower edges and two relatively shorter side edges. Each panel is connected to at least one adjacent panel along an elongated edge. A patch of adhesive is disposed on: the first surface of a first one of the panels; and another patch of adhesive is disposed on: the first surface on one of the other panels; or the second surface of said first one of the panels. The slave panels are each foldable along an elongated edge so that a surface of each slave panel is brought into confronting facial adjacency to and adhered against a surface of the master panel.

This application claims the benefit of priority to the following four(4) U.S. Provisional Applications:

-   -   61/001,859, filed Nov. 5, 2007    -   61/001,846, filed Nov. 5, 2007    -   61/001,845, filed Nov. 5, 2007    -   61/001,863, filed Nov. 5, 2007

FIELD OF THE INVENTION

The present invention is directed to a multi-panel blank having parallelpanel axes for a collapsible field director structure.

CROSS REFERENCE TO RELATED APPLICATION

Subject matter disclosed herein is disclosed in the following copendingapplication filed contemporaneously herewith and assigned to theassignee of the present invention;

Collapsible Field Director Assembly, filed as Ser. No. 12/263,709.

BACKGROUND OF THE INVENTION

Microwave ovens use electromagnetic energy at frequencies that vibratemolecules within a food product to produce heat. The heat so generatedwarms or cooks the food. To achieve surface browning and crisping of thefood a susceptor may be placed adjacent to the surface of the food. Atypical susceptor comprises a lossy metallic layer on a substrate. Whenexposed to microwave energy the material of the susceptor is heated to atemperature sufficient to cause the food's surface to brown and crisp.It is a common practice to include a susceptor in the packaging of thefood product.

Variations in the intensity and the directionality of theelectromagnetic field energy often form relatively hot and cold regionswithin the microware oven. These hot and cold regions cause the food towarm or to cook unevenly. If a microwave susceptor material is presentthe browning and crisping effect is similarly uneven.

One expedient to counter these uneven effects is the use of a turntable.The turntable rotates a food product along a circular path within theoven. This action exposes the food to a more uniform level ofelectromagnetic energy. However, the averaging effect produced by theturntable's rotation occurs along circumferential paths within the ovenand not along radial paths. Thus, even with the use of the turntablebands of uneven heating within the food are still created.

This effect may be more fully understood from the diagrammaticillustrations of FIGS. 1A and 1B.

FIG. 1A is a plan view of the interior of a microwave oven showing fiveregions (H₁ through H₅) of relatively high electric field intensity(“hot regions”) and two regions C₁ and C₂ of relatively low electricfield intensity (“cold regions”). A food product F having any arbitraryshape is disposed on a susceptor S which, in turn, is placed on aturntable T. The susceptor S is suggested by the dotted circle while theturntable is represented by the bold solid-line circle. Threerepresentative locations on the surface of the food product F areillustrated by points J, K, and L. The points J, K, and L arerespectively located at radial positions P₁, P₂ and P₃ of the turntableT. As the turntable T rotates each point follows a circular path throughthe oven, as indicated by the circular dashed lines.

As may be appreciated from FIG. 1A during one full revolution point Jpasses through a single hot region H₁. During the same revolution thepoint K passes through a single smaller hot region H₅ and one coldregion C₁. The point L experiences three hot regions H₂, H₃ and H₄during the same rotation. Rotation of the turntable through one completerevolution thus exposes each of the points J, K, and L to a differenttotal amount of electromagnetic energy. The difference in energyexposure at each of the three points during one full rotation isillustrated by the plot of FIG. 1B.

Owing to the number of hot regions encountered and cold regions avoidedpoints J and L experience considerably more energy exposure than PointK. If the region of the food product in the vicinity of the path ofpoint J is deemed fully cooked, then the region of the food product inthe vicinity of the path of point L is likely to be overcooked orexcessively browned (if a susceptor is present). On the other hand theregion of the food product in the vicinity of the path of point K islikely to be undercooked.

Another expedient to counter the undesirable presence of hot and coldregions is to employ a field director structure, either alone or incombination with a susceptor.

The field director structure includes one or more vanes, each having anelectrically conductive portion on a support of paperboard or othernonconductive material. The electrically conductive portions of thefield director structure mitigate the effects of regions of relativelyhigh and low electric field intensity within a microwave oven byredirecting and relocating these regions so that food warms and cooksmore uniformly. When used with a susceptor the field director structurecauses the food to brown more uniformly.

When an electrically conductive portion of a vane of the field directoris placed in the vicinity of either an inherently lossy food product ora lossy layer of a susceptor attenuation of certain components of theelectric field occurs. This attenuation effect is most pronounced whenthe distance between the electrically conductive portion of the fielddirector and the lossy element (either the lossy food product or thelossy layer of the susceptor) is less than one-quarter (0.25)wavelength. For a typical microwave oven this distance is about threecentimeters (3 cm). This effect is utilized by the prior art fielddirector structure to redirect and relocate the regions of relativelyhigh electric field intensity within a microwave oven.

FIG. 1C is a stylized plan view, generally similar to FIG. 1A,illustrating the effect of a vane V of a field director as it is carriedby a turntable T in the direction of rotation shown by the arrow. Thevane V is shown in outline form and its thickness is exaggerated forclarity of explanation.

Consider the situation at angular Position 1, where the vane V firstencounters the hot region H₂. Due to one corollary of Faraday's Law ofElectromagnetism only an electric field vector having an attenuatedintensity is permitted to exist in the segment of the hot region H₂overlaid by the vane V. However, even though only an attenuated field ispermitted to exist the energy content of the electric field cannotmerely disappear. Instead, the attenuating action in the region adjacentto the conductive portion of the vane manifests itself by causing theelectric field energy to relocate from its original location A to adisplaced location A′. This energy relocation is illustrated by thedisplacement arrow D.

As the rotational sweep carries the vane V to angular Position 2 asimilar result obtains. The attenuating action of the vane V againpermits only an attenuated field to exist in the region adjacent to theconductive portion of the vane. The energy in the electric fieldoriginally located at location B displaces to location B′, as suggestedby the displacement arrow D′.

The overall effect of the point-by-point attenuating action produced bythe passage of the vane V through the region H₂ is the relocation ofthat region H₂ to the position indicated by the reference character H₂′.Similar energy relocations and redirections occur as the vane V sweepsthrough all of the regions H₁ through H₅ (FIG. 1A) of relatively highelectric field intensity.

FIG. 1D is a plot showing total energy exposure for one full rotation ofthe turntable at each discrete point J, K and L. The correspondingwaveform of the plot of FIG. 1B is superimposed in FIG. 1D as a dottedline thereover.

It is clear from FIG. 1D that the presence of a field director resultsin a total energy exposure that is substantially uniform. As a resultwarming and cooking of a food product placed on the field director willbe improved over the situation extant in the earlier prior art.Similarly, the use of a field director in conjunction with a susceptorimproves uniformity of browning of a food product.

If inadvertently used in an “unloaded” microwave oven (i.e., an ovenwithout a food product or other article being present) problems ofoverheating of the susceptor assembly and overheating and arcing of thefield director have been observed. These problems are prevented when theconductive portions are appropriately configured and positioned on thevanes of the field director.

In view of the beneficial results provided by a field director, it isbelieved desirable to include a field director structure or a susceptorassembly that includes a field director within the packaging of the foodproduct or other article. However, inclusion of the field directorstructure or susceptor assembly should be effected in a manner that doesnot increase unduly the volume occupied by the packaging.

Accordingly, in view of the foregoing it is believed advantageous toprovide a field director structure or a susceptor assembly including afield director structure amenable for inclusion with a food product orother article in a way that minimizes the amount of packaging materialneeded for the package and which minimizes both the transport anddisplay volume occupied by the package.

SUMMARY OF THE INVENTION

The present invention is directed to a method of forming a collapsiblefield director structure from a blank comprising a sheet ofnonconductive material having at least three panels thereon. One of thepanels is a master panel and the other two panels are slave panels, themaster panel and each slave panel having a front surface and a rearsurface, the master panel and both slave panels each having at least twospaced-apart conductive regions thereon.

Each panel is substantially rectangular in shape, has elongated edges,and is connected to at least one adjacent panel along an elongated edge.The master panel has a line of articulation formed thereon extendinggenerally parallel to the upper edge thereof and subdividing the masterpanel into a mounting flange portion and a remainder portion. Theremainder portion has a fold line formed thereon subdividing theremainder portion into a spacer section and a conductor section.

The method comprises the steps of: folding the spacer and conductorsections with respect to each other to dispose the surface of thesections in confronting facial relationship; adhering the confrontingsurfaces of the spacer and conductor sections to each other thereby todefine a double-thickness conductor flap having a front surface and arear surface; folding the double-thickness conductor flap and one of theslave panels with respect to each other to dispose the front surface ofthe conductor flap in confronting facial adjacency to the rear surfaceof said one slave panel; folding the conductor flap of the conductorflap and the other slave panel with respect to each other to dispose therear surface of the conductor flap and the rear surface of said otherslave panel in confronting facial adjacency; adhering the front surfaceof the conductor flap to the rear surface of said one slave panel; andadhering the rear surface of the conductor flap to the rear surface ofsaid other slave panel.

The mounting flange may be attached to a planar support element to forma collapsible field director structure. A susceptor assembly having acollapsible field director structure may alternatively be formed byattaching the mounting flange of the master vane of the field directorstructure to a planar susceptor instead of a planar support element.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription, taken in connection with the accompanying drawings, whichform a part of this application and in which:

FIG. 1A is a plan view showing regions of differing electric fieldintensity within a microwave oven and showing the paths followed bythree discrete points J, K, and L located at respective radial positionsP₁, P₂ and P₃ on a turntable;

FIG. 1B is a plot showing total energy exposure for one full rotation ofthe turntable at each of the discrete points identified in FIG. 1A;

FIG. 1C is a plan view, generally similar to FIG. 1A, showing the effectof the field director structure upon regions of high electric fieldintensity and again showing the paths followed by three discrete pointsJ, K, and L located at respective radial positions P₁, P₂ and P₃ on aturntable;

FIG. 1D is a plot, similar to FIG. 1B, showing total energy exposure forone full rotation of the turntable at each discrete point, with thewaveform of FIG. 1B superimposed for ease of comparison;

FIG. 2 is a perspective view illustrating a susceptor assembly/fielddirector assembly incorporating a field director structure in accordancewith the present invention with the field director structure in thedeployed state;

FIGS. 3A, 3B and 3C are sectional views taken along respective sectionlines 3A-3A, 3B-3B and 3C-3C of FIG. 2 illustrating alternative forms oflocking tabs for a field director structure in accordance with thepresent invention;

FIG. 3D is a sectional view taken along section lines 3D-3D of FIG. 2illustrating a master vane for a field director structure in accordancewith the present invention;

FIG. 4 is a perspective view of the underside of the susceptorassembly/field director assembly of FIG. 2 illustrating the fielddirector structure in its collapsed state wherein the vanes are foldedtogether so that the field director structure occupies a generallyplanar disposition;

FIG. 5 is a plan view of the underside of the susceptor assembly/fielddirector assembly of FIG. 2 illustrating the field director structure ina disposition intermediate the collapsed and deployed states in whichthe master vane is articulated with respect to its flange and to thesusceptor/support member but before the slave vanes are displaced fromthe master vane and engaged with the susceptor/support member;

FIG. 6A is a view of a multi-panel sheet blank with parallel panel axesfor forming a collapsible field director structure of the presentinvention;

FIGS. 6B and 6C are perspective views taken along view lines directedfrom the bottom front of the sheet blank of FIG. 6A illustrating thevarious steps in forming a collapsible field director structure of thepresent invention from that blank;

FIG. 6D is a sectional view taken along section lines 6D-6D in FIG. 6Cafter completion of the steps of FIGS. 6B and 6C showing a collapsiblefield director structure of the present invention as formed from thatblank; and

FIGS. 7A and 7B are diagrammatic views of a manufacturing process forforming a collapsible field director structure using the blank of FIG.6A and for forming a susceptor assembly therefrom.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the following detailed description similar referencecharacters refer to similar elements in all figures of the drawings.

FIG. 2 is a pictorial perspective view illustrating either a susceptorassembly generally indicated by the reference character 10 or a fielddirector assembly generally indicated by the reference character 11.Each assembly includes a collapsible field director structure generallyindicated by the reference character 14 in accordance with the presentinvention. An assembly 10/11 incorporating the field director structure14 is useful in heating a food product or other article in a microwaveoven M.

The microwave oven M is suggested only in outline form in FIG. 2. ASource in the oven M produces an electromagnetic wave having apredetermined wavelength. A typical oven operates at a frequency of 2450MHz producing an electromagnetic wave having a wavelength on the orderof twelve (12) centimeters (about 4.7 inches). The walls W of the oven Mimpose boundary conditions that cause the distribution ofelectromagnetic field energy within the volume of the oven to vary. Thisgenerates a standing wave energy pattern within the volume of the oven.In the same manner as is explained in the Background of this applicationthe field director structure 14 is useful for redirecting and relocatingregions of higher and lower electric field intensity of the standingwave pattern within the volume of the oven. When used in conjunctionwith a turntable T (suggested in outline form in FIG. 2) the positionsof the redirected and relocated regions change continuously, to effectmore uniform tempering, thawing and cooking of a food product or otherarticle. Tempering is the warming of a food product, typically meat,from a sub-zero temperature (e.g., −40° F.) to about freezing (32° F.).To effect browning or crisping of a food product or other article asusceptor assembly having a conventional susceptor S is used inconjunction with the field director structure 14.

As will be developed the field director structure 14 in accordance withthe invention is convertible from a collapsed to a deployed state. Inthe deployed state (shown in FIG. 2) the field director structure 14occupies a self-supported disposition oriented generally orthogonal withrespect to a planar element of the assembly 10/11. In this dispositionthe field director structure 14 is able to perform its function ofredirecting and relocating the regions of higher or lower fieldintensity. In the collapsed state (shown in FIG. 4) the field directorstructure 14 occupies a generally planar disposition which facilitatesthe inclusion of an assembly 10/11 incorporating the field directorstructure 14 within the packaging of the food product or other article.

As noted each of the susceptor assembly 10 and the field directorassembly 11 includes a generally planar element. In the case of asusceptor assembly 10 the planar element takes the form of a generallyplanar susceptor 12 (FIG. 2). For a field director assembly 11 thegenerally planar element takes the form of a nonconductive supportmember 13. The susceptor 12 and the support member 13 each have ageometric center indicated by the respective reference character12C/13C. A respective reference axis 10A/11A for the assembly 10/11extends through the respective geometric center 12C/13C of its planarelement 12/13.

Whether implemented in the form of a susceptor 12 or a support member 13the planar element has an array of various openings 15 disposedtherethrough. As will be more fully explained herein some of theopenings 15 may be configured as open-ended slots 15S (see also FIGS.3A, 3B, 4 and 5) that interrupt the periphery of the planar element12/13 or as variously shaped holes 15H (see also FIGS. 3C, 4) that aresurrounded by the material of the planar element. A suitable number ofappropriately positioned vent openings 15V (suggested in FIG. 2 with afuller array shown in FIG. 4) may also be provided through the susceptor12 or the support member 13 to allow the escape of moisture from a foodproduct or other article.

The susceptor 12 of the susceptor assembly 10, illustrated in detail Aof FIG. 2, comprises a electrically nonconductive substrate 12S havingan electrically lossy layer 12L thereon. It should be noted that in thedrawings electrically nonconductive material is illustrated by stipledshading and electrically conductive material is illustrated bycontinuous diagonal shading.

The layer 12L is typically a thin coating of vacuum deposited aluminum.The planar susceptor 12 shown in the Figures is generally circular inoutline although it may exhibit any predetermined convenient size andshape consistent with the food product or other article (not shown) tobe warmed, cooked or browned within the oven M. In the Figures the fielddirector structure 14 is disposed under the susceptor 12 although itshould be appreciated that these relative positions may be reversed.Whatever the respective relative positions of the field directorstructure 14 and the planar susceptor 12 the food product or otherarticle is typically placed in contact with the susceptor 12.

The substrate 12S of the susceptor 12 may be made from any of a varietyof materials conventionally used for this purpose, such as cardboard,paperboard, fiber glass, other composites, or a polymeric material suchas polyethylene terephlate, heat stabilized polyethylene terephlate,polyethylene ester ketone, polyethylene naphthalate, cellophane,polyimides, polyetherimides, polyesterimides, polyarylates, polyamides,polyolefins, polyaramids or polycyclohexylenedimethylene terephthalate.The substrate 12S may be omitted if the electrically lossy layer 12L isself-supporting.

In the case of a field director assembly 11 the nonconductive supportmember 13, illustrated in detail B of FIG. 2, is made from one of thesame nonconductive materials used to form the substrate 12S. The supportmember 13 may also take any convenient size and shape. The supportmember 13 defines a useful platform upon which a separate susceptor(e.g., a plate or sleeve as typically supplied with a food product) maybe placed.

The field director structure 14 includes a master vane 16M and at leasttwo slave vanes generally indicated by the reference character 16S. Ingeneral, any convenient number of slave vanes 1, 2, 3 . . . N may beused, depending upon the size of assembly 10/11. In the Figures thefield director 14 includes four slave vanes 16S¹, 16S², 16S³ and 16S⁴.The master vane 16M and each slave vane 16S has a first, front, surfacegenerally indicated by the reference character “F” and a second, rear,surface generally indicated by the reference character “R” appended as asuffix to the corresponding reference numeral (see FIG. 5).

As will be discussed in connection with the particular embodiment shownin FIGS. 6A through 6D the master vane 16M and pairs of slave vanes 16Sare each formed from generally rectangular shaped panels fabricated froma nonconductive substrate 16N (FIGS. 3A through 3D). The preferredmaterial suitable for the panel substrate is a paperboard available from

International Paper as Grade Code 1355, 0.017/180# Fortress Uncoated CupStock. However, any suitably stiff, embossable, electrical nonconductivematerial may be used for the vane substrate. One of the samenonconductive substrate materials as mentioned above for the susceptormay be used as the substrate for the panels that form the vanes. Thesubstrate 16N may have a fire retardant composition applied thereto.

The master vane 16M and each slave vane 16S have at least one (but mayhave more) electrically conductive region(s) 18. An electricallyconductive region 18 may be formed as a thin coating of vacuum depositedaluminum or as a foil adhered to the vane's surface. If a foil is usedit is desirable to fold the foil to produce at least double-thicknessabout its periphery.

As perhaps best shown in FIGS. 3A through 3D each electricallyconductive region 18 on each vane 16M, 16S has a first (inner) end 18D,a second (outer) end 18E, a top edge 18H and a bottom edge 18L. Theinner end 18D of a conductive region 18 is that end disposed closer tothe geometric center 12C/13C of the planar element of the assembly 10/11or the geometric center 16M-C of the master vane 16M (see FIG. 3D). Theelectrically conductive region 18 on each vane is sized such that thenonconductive substrate 16N of the vane is exposed about the perimeterof each electrically conductive region 18. The exposed substrate definesa top border 19T, a lower border 19L, a radially inner border 19D and aradially outer border 19E.

The longest distance between the first and second ends 18D and 18Edefines a predetermined length dimension L (FIG. 3A) for each conductiveregion 18. The shortest distance between the top edge 18H and the bottomedge 18L defines a predetermined width dimension W (FIG. 3B) for eachconductive region 18.

The width dimension W of the electrically conductive region 18 of a vaneshould be about 0.1 to about 0.5 times the wavelength generated in theoven. The length dimension L of the electrically conductive region 18 ofa vane should be at least about 0.25 times the wavelength of theelectromagnetic energy generated in the oven. A length dimension L abouttwice the wavelength of the electromagnetic energy generated in the ovendefines a practical upper limit.

Preferably each corner of each electrically conductive region 18 of eachvane is rounded at a radius dimension 18R (FIG. 3B). The radiusdimension 18R may be up to and including one-half of the width dimensionW of the conductive region 18 (i.e., 18R≦0.5 W).

The conductive region 18 of any vane 16M, 16S may be covered with anelectrically nonconductive material such as a dielectric tape or anonconductive polymeric spray coating (not shown). Suitable spraycoatings include a polyacrylic or a polytetrafluoroethylene spraycoating.

As best seen in FIG. 3D the master vane 16M is a relatively elongatedmember (as compared to a slave vane 16S) having a conductor flap 17C anda mounting flange 17G. The geometric center of the master vane 16M isindicated by the reference character 16M-C. As is explained more fullyhereinafter the conductor flap 17C of the master vane 16M may have adouble-thickness of substrate material. The double-thickness isindicated in the depiction of the master vane in FIG. 5 by the detail C.

Two non-contiguous electrically conductive regions 18 are provided onthe conductor flap 17C of the master vane (FIGS. 2, 3D). The conductiveregions 18 may be provided on either the front surface 17F of theconductor flap 17C (as illustrated in FIG. 3D) or the rear surface 17R(FIG. 3D) of the flap 17C, as is convenient. When the conductor flap 17Cof the master vane 16M has a double-thickness of substrate material, theconductive regions 18 may alternatively be sandwiched therebetween (FIG.5).

The conductive regions 18 may also be provided on either the frontsurface F or the rear surface R of each slave vanes 16S¹, 16S², 16S³ and16S⁴, as may be convenient. In FIGS. 3A-3D a single conductive region 18is shown on the front surface of each slave vane 16.

The flange 17G defines the link by which the master vane 16M isconnected to the undersurface of either the substrate 12S of thesusceptor 12 or to the planar support member 13.

The mounting flange 17G is separated from the conductor flap 17C of themaster vane 16M by a line of articulation 17B (FIGS. 2 and 4). Themounting flange 17G is secured such that the line of articulation 17Bextends generally along a diametrical dimension of the susceptor 12 orthe planar support member 13. Due to the presence of the line ofarticulation 17B the conductor flap 17C of the master vane 16M isarticulably movable with respect to either the susceptor 12 or thesupport 13, as is apparent from FIGS. 4 and 5.

Each slave vane 16S¹, 16S², 16S³ and 16S⁴ is connected (in a manner tobe described) to the master vane 16M. If pairs of slave vanes are formedon panels a panel carrying the slave vanes 16S¹, 16S⁴ is connected tothe rear surface 17C-R of the conductor flap 17C of the master vane 16M.Similarly, a panel carrying the slave vanes 16S², 16S³ is connected tothe front surface 17C-F of the conductor flap 17C of the master vane16M.

Each slave vane 16S¹, 16S², 16S³ and 16S⁴ is flexibly connected withrespect to the master vane 16M along a respective line of flexure 16L¹,16L², 16L³ and 16L⁴ (all seen in FIG. 5). The term “flexible”,“flexibly” (or similar terms) mean that that a slave vane may be foldedwith respect to the master vane along its line of flexure. It is notmeant to connote that the slave vane necessarily returns to its priorposition in a resilient manner.

The distal end of each slave vane 16S¹, 16S², 16S³ and 16S⁴ has arespective locking tab 16T¹, 16T², 16T³ and 16T⁴ thereon. Each lockingtab engages a respective opening 15 in the planar element 12/13.

A locking tab may exhibit any convenient shape suitable for engagementinto an opening 15. The locking tabs 16T¹ through 16T³ shown in FIGS. 3Athrough 3C are all generally trapezoidal in shape. Locking tab 16T¹,16T² and 16T⁴ are each respectively received within an open-ended slot15S that interrupts the periphery of the planar element 12/13. Theramped inner edge of the locking tab 16T² on the slave vane 16S²(indicated at reference character 15R in FIG. 3B) engages the planarelement 12/13 in a hooked manner. The locking tab 16T³ is shown as beingreceived within the hole 15H (FIGS. 2 and 3C).

Conversion From Collapsed to Deployed State As alluded to earlier thefield director structure 14 is convertible from a collapsed to adeployed state. The collapsed state of the field director 14 is shown inFIG. 4.

When the field director 14 is in the collapsed state the slave vanes16S¹, 16S⁴ fold along their respective lines of flexure 16L¹, 16L⁴ tobring these vanes into facial engagement against the rear surface 17C-R(best seen in FIG. 5) of the conductor flap 17C of the master vane 16M.Similarly, the slave vanes 16S², 16S³ fold along their respective linesof flexure 16L², 16L³ to bring these vanes into facial engagementagainst the front surface 17C-F of the conductor flap 17C of the mastervane 16M. With the slave vanes folded against opposed surfaces of themaster vane 16M the conductor flap 17C is able to fold along the line ofarticulation 17B into generally parallel relationship with the planarelement (i.e., either the susceptor 12 or the planar support member 13).Preferably the conductor flap 17C is folded along the line ofarticulation in a direction that disposes the conductor flap 17Csubstantially coplanar with the mounting flange 17G. However, the foldmay occur in a direction that causes the conductor flap 17C to overliethe mounting flange 17G (with the vanes 16S², 16S³ sandwichedtherebetween).

With the vanes 16M, 16S folded against each other the field directorstructure 14 as a whole is able to occupy a generally planar dispositionagainst the planar element of the susceptor assembly 10 or the fielddirector assembly 11. In this disposition the susceptor assembly 10 orthe field director assembly 11 incorporating the field directorstructure 14 occupies a minimal volume, thus facilitating its inclusionwithin a package of a food product or other article.

To transform the field director structure 14 into the deployed state theconductor flap 17C of the master vane 16M (and the slave vanes 16Sflexibly connected thereto) articulates with respect to the susceptor12/support element 13 in the direction of the arrows 21 (FIG. 4). At thecompletion of the articulated movement the vane 16M of the fielddirector 14 occupies an orientation in which it is substantiallyperpendicular to its flange 17G and thus, to the attached susceptor12/support element 13, as the case may be. The plane of each slave vane16S is oriented substantially perpendicular to the mounting flange ofthe master vane 16M. The plane of each slave vane intersects with theplane of the master vane along its respective line of flexure. Thisarrangement is illustrated in FIG. 5.

The slave vanes 16S then flexibly displace with respect to the mastervane 16M in the directions of the arrows 22 (FIG. 5) to angularly spacethe slave vanes from the master vane. Angular displacement continuesuntil the locking tabs 16T on the slave vanes 16S are received in theopenings 15 in the susceptor 12/support member 13. The slave vanes 16Seach originate from their point of origin along their respective linesof flexure 16L generally in the vicinity of the geometric center 12C/13Cand extend generally radially outwardly therefrom toward the receipt ofthe locking tabs 16T into the openings 15.

As shown in FIG. 2 when deployed the field director structure 14occupies a self-supported disposition oriented generally orthogonal withrespect to a planar element 12/13 of the assembly 10/11. The flexibleconnection of the slave vanes 16S with the master vane 16M permits thevanes 16M, 16S to cooperate with each other to form the self-supportingfield director structure in the deployed state. The receipt of a lockingtab 16T in an opening 15 in the planar element 12/13 holds the fielddirector structure 14 in the self-supported disposition.

Owing to the configuration and placement of the conductive regions 18 onthe vanes 16M, 16S when the field director 14 is deployed:

(1) the top edge 18H of each conductive region 18 of each vane 16M, 16Sis spaced a predetermined distance 23D (FIG. 3A) from thesusceptor/support element; and

(2) the inner end 18D of each conductive region 18 of each of the vanes16M, 16S is disposed a predetermined separation distance 23S (FIG. 2)from the geometric center 12C/13C of the planar susceptor 12 or thegeometric center 13C of the planar support member 13, as the case maybe. If the field director structure 14 is used without a planarsusceptor 12 or a planar support member 13 the separation distance 23Sis measured from the geometric center 16M-C (FIG. 3D) of the master vane16M.

The dimension 23D (FIG. 3A) measured in a direction orthogonal to theplane of the susceptor/support element lies in a range from 0.025 to 0.1times the wavelength of the standing electromagnetic wave produced inthe microwave oven in which the susceptor assembly 10 is being used.That is, the dimension 23D should be at least 0.025 times thewavelength. Further, the dimension 23D should be no greater than 0.1times that wavelength (that is, the dimension 23D≦0.1 times thatwavelength).

The separation distance 23S (measured in a direction parallel to theplane of the susceptor 12 or the support member 13) should be at least0.16 times the wavelength of the standing electromagnetic wave producedin the microwave oven in which the susceptor assembly 10 is being used.For the master vane 16M the distance 23S between an end 18D of aconductive region 18 thereon and the geometric center 12C/13C (or thegeometric center 16M-C) is measured along the surface of the master vane16M (FIG. 3D). Note, however, that for a slave vane 16S the distance 23Sis not measured along the surfaces of the slave vane but is measured asthe straight line distance between an end 18D of a conductive region 18on a slave vane 16S and the geometric center 12C/13C (or the geometriccenter 16M-C). This relationship is indicated in FIG. 2.

The relative placement of the conductive regions with respect to eachother and to the susceptor/support member provides beneficial advantagesif the field director were to be inadvertently used in an “unloaded”microwave oven (i.e., an oven without a food product or other articlebeing present). When a field director is placed in an unloaded oven andthe oven is energized deleterious problems of overheating of thesusceptor, and/or overheating of the field director structure, and/orarcing have been observed.

By “overheating of the susceptor” it is meant heating of the lossysusceptor material to the extent that the susceptor substrate burns.“Overheating of the field director structure” means heating of thepaperboard support of a vane to the extent that it burns. Suchoverheating may be caused by either the heat generated by a lossysusceptor material or by arcing. “Arcing” is an electrical dischargeoccurring when a high intensity electric field exceeds the breakdownthreshold of air. Arcing typically occurs in the vicinity of theelectrically conductive region(s) of the vanes, particularly along theedges, and especially at any sharp corners. Arcing may cause thesubstrate of a vane to discolor, to char, or, in the extreme, to igniteand to burn.

It has been found that disposing the first end 18D of the conductiveregion 18 of each of the vanes at the predetermined separation distance23S from the geometric center 12C of the planar susceptor 12 mitigatesoverheating of the susceptor in the vicinity of its center 12C.Additionally or alternatively, overheating has been found to bemitigated by disposing the electrically conductive region 18 of the vanethe predetermined close distance 23D from the electrically lossy layer12L of the planar susceptor 12 (however that spacing is achieved) (FIG.3A). Further mitigation of overheating of the susceptor may be achievedby the provision of the lower border 19L.

Disposing the electrically conductive region of a vane at thepredetermined close distance 23D from the electrically lossy layer 12Lof the planar susceptor 12 and rounding the corners of the conductiveregion 18 with the radius 18R have also been shown to mitigate arcing.

Disposing the first end 18D of the conductive region 18 of each of thevanes at the predetermined separation distance 23S from the geometriccenter 12C/13C of the planar element or from the geometric center 16M-Cof the master vane 16M also mitigates arcing between vanes in thisvicinity.

If the conductive region 18 of any of the vanes is covered with theelectrically nonconductive material, such a covering material mitigatesarcing at corners of the conductive region of the vane whether thecorners are squared or rounded. Alternatively or additionally, if theconductive region of a vane is implemented using a foil with foldededges the increased thickness of the perimeter of the conductive regionalso mitigates arcing.

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In another aspect the present invention is directed to a multi-panelblank from which a collapsible field director structure 14 (FIG. 2) inaccordance with the present invention may be formed. The blank is shownin FIG. 6A and is generally indicated by the reference character 100. Ingeneral, the blank 100 includes a nonconductive substrate having atleast three panels 102, 104 and 106 defined thereon. The panel 102defines a master panel and two of the panels 104, 106 define slavepanels. The master panel 102 and the slave panels 104, 106 are theprecursors of the master vane 16M and slave vanes 16S present in thefinished field director structure 14 (FIG. 2).

It should be understood that it lies within the contemplation of thepresent invention that a given multi-panel sheet having panels arrangedin the parallel configuration may contain additional panels beyond thoseillustrated which, when folded together and suitably adhered, to defineadditional vane(s).

Each panel 102, 104 and 106 is substantially rectangular in shape andincludes a pair of elongated edges indicated by the appended alphabeticsuffix “E¹” or “E²”, and a pair of relatively shorter side edgesindicated by the appended alphabetic suffix “Z¹” or “Z²”. A referenceaxis indicated by the reference character 102A, 104A, 106A respectivelyextends through each panel 102, 104, 106. The axes extend in a directiongenerally parallel to an elongated edge of a panel. The axes 102A, 104A,106A lie parallel to each other.

Fold lines 108, 110 are disposed between adjacent panels. The fold lines108, 110 extend generally parallel to an elongated edge of the slavepanels (e.g., edges 104E¹, 106E²) so that the respective axes 102A,104A, 106A of the panels 102, 104, 106 are substantially parallel toeach other. Each panel is connected to at least one adjacent panel alongan elongated edge. It is noted that the fold lines 108, 110 do notextend across the full breadth of the panels to permit the panels tofold in the manner to be described. The panels are foldable relative toeach other along the fold lines 108, 110 so that a surface of each slavepanel may be brought into confronting facial adjacency to a surface ofthe master panel where it is held thereagainst by the adhesive.

Each slave panel 104, 106 has a locking tab 104T, 106T disposed at eachend of one elongated edge thereof. The tabs are disposed along oppositeelongated edges so that, after folding, the tabs 104T, 106T will bepositioned adjacent to the planar member 12/13 to engage the openings 15therein.

It is noted that the number of slave panels in a blank depends upon thenumber of slave vanes used in the field director structure 14. Thus, inFIG. 6A each blank includes two slave panels 104, 106 from which thefour slave vanes 16S¹, 16S², 16S³ and 16S⁴ (FIG. 2) are formed.

The master panel 102 has a line of articulation 102B formed thereon. Theline of articulation 102B extends generally parallel to an elongatededge (e.g., edge 102E¹) of the master panel 102. The line ofarticulation 102B subdivides the master panel 102 into a mounting flangeportion 102G and a remainder portion 102C. The line of articulation 102Bcorresponds to the line of articulation 17B of master vane 16M discussedin connection with FIGS. 2 through 5.

As seen in FIG. 6A a fold line 102L is formed into the remainder portion102C. The fold line 102L subdivides the remainder portion 102C into aspacer section 102S and a conductor section 102Y. The surfaces of thespacer section 102S and the conductor section 102Y presented for view inFIG. 6A are respectively indicated by reference characters 102 j ¹ and102 j ². Either or both of these surfaces 102 j ¹ and 102 j ² may havean adhesive material thereon for a purpose to be described.

Each panel 102, 104 and 106 has a front surface, indicated by thealphabetic suffix “F” appended to the appropriate reference numeral anda rear surface indicated by the appended alphabetic suffix “R”.

The respective front and rear surfaces “F”, “R” of the panels 104 and106 will eventually define the respective front surface F and rearsurface R of the slave vanes 16S into which these panels are formed.

As will be developed, because a preliminary operation is required toform the conductor flap 17C of the master vane from the blank 100,spaced areas on the rear surface 102R of the panel 102 (FIG. 6A) willeventually define the respective front surface 17F and rear surface 17R(FIG. 3D) of the conductor flap 17C of the master vane 16M. These spacedareas are located on the rear surface of the panel 102 opposite to thesurface 102 j ¹ of the spacer section 102S and on the rear surface ofthe panel 102 opposite to the surface 102 j ² of the conductor section102Y, respectively. In particular the reverse side of the surface 102 j¹ will eventually define the rear surface 17R of the conductor flap 17C(FIGS. 5, 6D) while the reverse side of the surface 102 j ² of theconductor section 102Y will eventually define the front surface 17F ofthe conductor flap 17C (FIGS. 5, 6D).

The conductor section 102Y of the remainder portion 102C of the masterpanel 102 and both slave panels 104, 106 each have at least twospaced-apart conductive regions 118-1 and 118-2 thereon. Theseconductive regions 118-1 and 118-2 are the precursors of the conductiveregions 18 disposed on the master vane 16M and the slave vanes 16S asdiscussed earlier. Although, in principle, the conductive regions may bedisposed on either a front surface F, a rear surface R, or bothsurfaces, of a given panel, it may be more convenient to manufacture ablank by disposing all of its conductive regions on the same surface ofa panel.

The region on any panel between the spaced-apart conductive regions118-1 and 118-2 defines a land portion indicated by the appendedalphabetic suffix “P”. Flexure lines denoted by an appended alphabeticsuffix “L” are scored into one surface of each slave panel between theconductive regions thereon. These flexure lines are the precursors ofthe flexure lines 16L of the slave vanes 16S.

As will be discussed a patch of an adhesive material is disposed on thefirst surface of a first one of the three panels. In addition, anotherpatch of adhesive material is disposed on either: the first surface onone of the other panels; or, the second surface of said first panel. InFIG. 6A the locations of the adhesive patches are demarcated bydot-dashed lines and denoted by an appended alphabetic suffix “H”. Theadhesive must be disposed between the flexure lines L of the slavepanels to insure that the slave panels may be properly deployed to formthe structure shown in FIG. 2.

The adhesive may be applied in any convenient form. Any adhesivematerial commonly used for microwave susceptors may be used for each orboth of the patches. Suitable adhesives include that manufactured byHenkel Adhesives, Elgin, Ill., and sold as type 45-6120 or thosemanufactured by Basic Adhesives, Inc., Brooklyn, N.Y. and sold as typesBR-3885 or BR-4736.

Any one of the following combinations of surfaces provides the minimumessential adhesive placements to implement these requirements for theconstruction of a field director structure from the parallel blank 100:

-   -   a) the front surface 102F and the rear surface 102R of the        master panel 102; or    -   b) the front surface 102F of the master panel 102 and the rear        surface 106R of the slave panel 106; or    -   c) the rear surface 104R of the slave panel 104 and the rear        surface 106R of the slave panel 106; or    -   d) the rear surface 102R of the master panel 102 and the rear        surface 104R of the slave panel 104.

Other combinations of surfaces may be used for the placements ofadhesives. However, these combinations result in extra adhesive beingdisposed on confronting surfaces when a slave panel is brought intoconfronting facial adjacency to a surface of the master panel. In thefollowing listed combinations, the surfaces having the additionaladhesive are indicated by the asterisk (*). These additionalcombinations are:

-   -   e) the front surface 102F* and the rear surface 102R of the        master panel 102 and the rear surface 104R* of the slave panel        104; or    -   f) the front surface 102F and the rear surface 102R* of the        master panel 102 and the rear surface 106R* of the slave panel        106; or    -   g) the rear surface 102R* and the rear surface 104R of the slave        104 and the rear surface 106R* of the slave panel 106; or    -   h) the front surface 102F* and the rear surface 104R of the        slave 104 and the rear surface 106R* of the slave panel 106; or    -   i) the front surface 102F* and the rear surface 102R* of the of        the master panel 102, the rear surface 104R* of the slave panel        104 and the rear surface 106R* of the slave panel 106.

The method by which a blank 100 configured in the parallel configurationmay be fashioned into a field director structure 14 may be understoodfrom the sequence of drawings shown in FIGS. 6B through 6D. The viewspresented in FIGS. 6B and 6C are also as seen looking upwardly andrearwardly from a viewpoint located below the bottom front of theparallel blank of FIG. 6A.

The preliminary operation mentioned above that forms the conductor flap17C from the remainder portion 102C of the master panel 102 is shown inFIG. 6B. An adhesive material 102 k (shown by the dot-dashed outline) isdisposed over the majority of the surface 102 j ¹ of the spacer section102S. The same adhesive material as used for the other patches may beused here. The surfaces 102 j ¹ and 102 j ² of the master panel arefolded along the fold line 102L into confronting facial adjacency. Thisfold is indicated by the arrow 160.

Once brought into facial adjacency the surfaces 102 j ¹ and 102 j ² areadhered together to form the conductor flap that corresponds to the flap17C (FIGS. 3D, 6D). The conductor flap 17C thus has a double-thicknessof substrate material, as also depicted by the detail view C in thedrawing FIG. 5. Opposed surfaces of the double-thickness conductor flap17C define the front surface 17F and the rear surface 17R of the mastervane 17, as is apparent from examination of FIG. 6D.

Next (FIG. 6C), the now-formed master vane 17 and the slave panel 104are folded relative to each other along the fold line 108 to bring thefront surface 17F of the conductor flap 17C of the now-formed mastervane 17 and the rear surface 104R of the slave panel 104 intoconfronting facial adjacency. This folding action is indicated by thereference arrow 164.

In the next step (also seen in FIG. 6C) the slave panel 106 is foldedalong the fold line 110 to bring its rear surface 106R into confrontingfacial adjacency with the rear surface 17R on the conductor flap 17C ofthe now-formed master vane 17 (FIGS. 6B and 6D). The folding action isindicated in FIG. 6C by the reference arrow 166.

The fully folded collapsible field director structure is shown in thesectional view of FIG. 6D. The surfaces 17F/104R and the surfaces17R/106R are adhered together by the appropriately positioned adhesivematerials 104H and 106H (shown as respectively disposed on the rearsurfaces of the panels 104 and 106) (minimum alternative c) as describedabove. The mounting flange of the field director structure so completedmay be attached to a planar support element, as will be discussed.Alternatively, a susceptor structure having a collapsible field directorstructure may be formed by attaching the mounting flange to a planarsusceptor instead of a planar support element, as will also bediscussed.

It should be appreciated that the steps of the method may be performedin alternative order or may be performed simultaneously. For instancethe folding and adhering steps may performed in a different sequence,e.g., the slave panel 104 may be folded against the conductor section102Y and adhered thereto, then the conductor section 102Y may be foldedagainst the spacer section 102S and adhered thereto and finally theslave panel 106 may be folded against the spacer section 102S andadhered thereto.

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Manufacturing Process Description FIG. 7A is a diagrammatic view of amanufacturing process generally indicated by the reference character 200for forming multiple collapsible field director structures 14 from anarray 100P of preform blanks 100 each configured as shown in FIG. 6A. InFIG. 7A the array 100P is shown to have a top and a bottom row of blanks100P-T, 100P-B. FIG. 7B is a diagrammatic view of a manufacturingprocess generally indicated by the reference character 202 for formingmultiple susceptor assemblies 10 each having a susceptor 12 and acollapsible field director structure 14.

The individual sheet blanks in the array 100P may be arranged in anydesired orientation. For example, although the blanks are shown in FIG.7A with the flanges 102G of the blanks in both rows 100P-T, 100P-Boriented toward a first elongated edge of the array, to conserveconductive material the orientation of the flanges 102G of the blanks inthe bottom row 100P-B may be reversed so that the flanges 102G of theblanks in bottom row 100P-B are oriented toward the second elongatededge of the array. Alternatively, the blanks may be rotated so that theflanges are oriented orthogonal to the elongated edges of the array.

To form the field director structures 14 a roll 206R of a foil-filmlaminate 206 and a roll 220R of substrate material 220 (e.g.,paperboard) are supplied to a laminating/die cutting apparatus 230. Thefoil-film laminate 206 is comprised of a metal foil 206F and a polymericfilm 206P. An adhesive 240 is applied in a predetermined pattern to thefoil side 206F of the foil-film laminate 206 by a roll assembly 225.Alternatively, the adhesive 240′ may be applied in a predeterminedpattern to the substrate material 220 by a roll assembly 225′. Thepattern of adhesive 240 (or 240′) is applied to the foil 206F (or thesubstrate web 220) in those areas eventually to be occupied by theconductive regions 118 on the panels 102, 104, 106.

The laminating/die cutting apparatus 230 adheres the foil 206F to thesubstrate material 220, die cuts the foil/film laminate 206 along theperimeters of the conductive regions 118, and strips away the un-adheredfoil/film laminate 206U. The un-adhered foil/film laminate 206U iscollected by a roll 235.

The laminating/die cutting apparatus 230 scores the paperboard to definethe fold lines 108, 110, the lines of articulation 102B and the flexurelines 104L, 106L (FIG. 6A). The laminating/die cutting apparatus 230also die cuts the substrate along perimeter lines to form the preformarray 100P. For clarity an enlarged plan view of this array 100P ofsheet blank preforms is shown at the top left region of FIG. 7A.

The array 100P of sheet blank preforms is fed to a die cutting apparatus250 which die cuts the array 100P along perimeter lines of theindividual sheet blanks 100 to form an array 100A of individual sheetblanks 100. An enlarged plan view of this array 100A of sheet blanks isalso shown at the top right region of FIG. 7A.

The array 100A of individual sheet blanks 100 is then fed to a gluingand folding apparatus 260. The gluing and folding apparatus 260 appliesadhesive in the patches 102H, 104H and/or 106H, as previously describedin conjunction with FIGS. 6A through 6D.

Each individual sheet blank 100 is folded and glued together in themanner as shown in FIGS. 6B through 6D. The sheet blanks 100 may then betrimmed by a trimming apparatus 270 to form an array 14A of fielddirector structures 14-1, 14-2, . . . 14-N. The field directorstructures 14 in the array 14A may be still attached to each other atseveral corner points to facilitate handling.

FIG. 7B shows the forming of the susceptor assemblies 10. A series ofsusceptors 12 is created and adhered to the field director structures 14to form the susceptor assemblies 10.

The formation of the susceptor 12 is shown in the block diagram at theleft of the FIG. 7B. As indicated in block 300 a lossy layer 12L (FIG.2) is formed by vacuum metallizing a polymeric film [e.g.,heat-stabilized polyethylene terepthalate (PET)]. The lossy layer 12Lthus formed is laminated to a suitable substrate 12S to form a laminatestructure as shown at block 310. This laminate structure is then die-cut(block 320) in the desired shape to form a series of susceptors 12 (twosusceptors 12-1 and 12-2 are shown).

Individual die-cut susceptors 12 and the individual ones, e.g., 14-1,14-2, of the array 14A of field director structures 14 are adheredtogether to form a susceptor assembly 10. The individual field directorstructures 14 are separated from the array 14A and each glued to acorresponding susceptor 12 in the area of the flange 17G (see also FIGS.4 and 5). In FIG. 7B one susceptor assembly 10-1 is shown as alreadyassembled. A second susceptor assembly 10-2 is being assembled byadhering the flange of a second field director structure 14-2 to asecond susceptor 12-2.

Each completed susceptor assembly 10 with its field director structure14 in the collapsed state is suitable for inclusion in the package of afood product or other article.

If a field director assembly 11 (not having a susceptor) is to beformed, each field director structure 14 may be attached to a planarsupport element 13.

Method of Use When the package containing the food product or otherarticle is opened by the consumer, the susceptor assembly 10 (or fielddirector assembly 11) with the field director structure 14 in itscollapsed state is removed from the package. In the collapsed state thevanes 16 of the field director structure 14 are folded flat against thesusceptor 12 (or planar support element 13) as seen in FIG. 4.

To deploy the field director structure 14 the master vane 16M isarticulably moved away from the planar susceptor 12 along the line ofarticulation 17B on the flange 17G so that the vanes 16M, 16S areoriented orthogonally to the plane of the susceptor 12 (or planarsupport element 13) and to the flange 17G (FIG. 5). The slave vanes 16Sare then flexibly displaced in an angular direction from the master vane16M (arrows 22, FIG. 5) along the respective lines of flexure 16L untilthe locking tabs 16T engage the openings 15 in the planar susceptor 12(or planar support element 13) (see FIG. 2).

When deployed the field director structure 14 occupies a self-supporteddisposition oriented generally orthogonal with respect to the mountingflange 17G and the susceptor 12 of the assembly 10 (or planar supportelement 13 of the field director assembly 11).

By virtue of the flexible connection of the slave vanes 16S with themaster vane 16M, the vanes 16M, 16S cooperate with each other to formthe self-supporting field director structure when deployed. Due to thereceipt of a locking tab 16T within an opening 15 in the susceptor 12(or planar support element 13), the field director structure 14 is heldin the self-supported disposition.

The fully deployed assembly 10/11 is then placed in the microwave ovenwith the susceptor 12 (if used) in contact with the food product orother article for subsequent heating, cooking, or browning. If the ovenincludes the turntable T (FIG. 2), the fully deployed assembly 10/11(with the food product or other article thereon) is placed on theturntable.

When energized the oven produces a standing electromagnetic wave havinga predetermined wavelength. As explained in connection with FIGS. 1A-1D,in the presence of the standing electromagnetic wave only an attenuatedelectric field component of the electromagnetic wave exists in a planetangent to the conductive region of each vane. The attenuation of theelectric field component of the electromagnetic wave results inenhancement of the component of the electric field substantiallyorthogonal to the conductive region of each vane.

The attenuating action manifests itself by causing the electric fieldenergy to relocate on the planar susceptor 12. The presence of anassembly 10/11 having the field director structure 14 thus results in atotal energy exposure that is substantially uniform. As a result,warming, cooking and browning of a food product or other article placedon the assembly 10/11 will be improved over the situation extant in theprior art.

Those skilled in the art, having the benefit of the teachings of thepresent invention may impart modifications thereto. Such modificationsare to be construed as lying within the scope of the present invention,as defined by the appended claims.

What is claimed is:
 1. A method of forming a collapsible field directorstructure from a blank comprising: a sheet of nonconductive materialhaving at least three panels thereon, one of the panels being a masterpanel and the other two panels being first and second slave panels, themaster panel and each slave panel having a front surface and a rearsurface, the master panel and both slave panels each having at least twospaced-apart conductive regions thereon, each panel being substantiallyrectangular in shape and having elongated edges, each panel beingconnected to at least one adjacent panel along an elongated edge, themaster panel having a line of articulation formed thereon, the line ofarticulation extending generally parallel to the upper edge thereof andsubdividing the master panel into a mounting flange portion and aremainder portion, the remainder portion having a fold line formedthereon, the fold line subdividing the remainder portion into a spacersection and a conductor section, the method comprising the steps of: a)folding the spacer and the conductor sections with respect to each otherto dispose surfaces of these sections in confronting facialrelationship; b) adhering the confronting surfaces of the spacer and theconductor sections to each other thereby to define a double-thicknessconductor flap having a front and a rear surface; c) folding thedouble-thickness conductor flap and the first slave panel with respectto each other to dispose the front surface of the conductor flap inconfronting facial adjacency to the rear surface of said first slavepanel; d) folding the double-thickness conductor flap of the masterpanel and the other slave panel with respect to each other to disposethe rear surface of the conductor flap and the rear surface of saidother slave panel in confronting facial adjacency; e) adhering the frontsurface of the conductor flap to the rear surface of said one slavepanel; and f) adhering the rear surface of the conductor flap to therear surface of said other slave panel.
 2. The method of claim 1 furthercomprising the step of: g) attaching the mounting flange to a planarsupport element.
 3. A method of forming a susceptor assembly having acollapsible field director structure from a blank comprising: a sheet ofnonconductive material having at least three panels thereon, one of thepanels being a master panel and the other two panels being first andsecond slave panels, the master panel and each slave panel having afront surface and a rear surface, the master panel and both slave panelseach having at least two spaced-apart conductive regions thereon, eachpanel being substantially rectangular in shape and having elongatededges, each panel being connected to at least one adjacent panel alongan elongated edge, the master panel having a line of articulation formedthereon, the line of articulation extending generally parallel to theupper edge thereof and subdividing the master panel into a mountingflange portion and a remainder portion, the remainder portion having afold line formed thereon, the fold line subdividing the remainderportion into a spacer section and a conductor section, the methodcomprising the steps of: a) folding the spacer and the conductorsections with respect to each other to dispose surfaces of thesesections in confronting facial relationship; b) adhering the confrontingsurfaces of the spacer section and the conductor sections to each otherthereby to define a double-thickness conductor flap having a front and arear surface; c) folding the double-thickness conductor flap and thefirst slave panel with respect to each other to dispose the frontsurface of the conductor flap in confronting facial adjacency to therear surface of said first slave panel; d) folding the double-thicknessconductor flap of the conductor flap and the other slave panel withrespect to each other to dispose the rear surface of the master paneland the rear surface of said other slave panel in confronting facialadjacency; e) adhering the front surface of the conductor flap to therear surface of said one slave panel; f) adhering the rear surface ofthe conductor flap to the rear surface of said other slave panel; and g)attaching the mounting flange to a planar susceptor.